TBIThrottle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.
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I'm tring to solve the hot run problem 305 TBI's have. Whats the lowest temp thermastat can I run and still be compatible with the computer? Also, how can you convert to a dual fan setup (like the Z28's).
The coldest temp thermostat I've seen is a 160º. But a lower temp thermostat wont solve an overheating problem. Check to make sure your air dam is in place. Check to make sure your radiator is free from debris sticking into it. Also check between your radiator and AC condensor for debris. Leaves and plastic bags get in between there. Lastly, you can change your fan coolant switch (bottom passenger side of the block) for a lower-temp one, that will turn on your fan sooner.
thermostat temp wont make a difference if its running hot, once the car gets above the thermostat open temp the thermostat stays open, what you need to do is increase airflow over the radiator, check your airdam, and get a lower temp fan switch or wire it to run all the time if you live somewhere real hot
you want to maintain a 180 degree water temp, lower gives less reliable performance and starts to get into alot of the warm up code of the factory chip calibration
The only reason people say they run hot from the factory is because factory setting for the fan to come on is like 225*F. As for actually running hot, as long as I have a fan on, my temp never goes above 160*, and because of that, I freeze my @ss off in the winter. I may put a 195* back in before spring comes. I have too long of a drive to work to have my teeth chatter all the way.
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I have to agree with Pablo, a 160* Tstat causes more harm than good. Until I got into PROM burning, I was a strong advocate of a 160* Tstat, especially for TPI cars. With TBI cars, I still felt a 180* Tstat was better as it has a wet manifold and needs some of the heat of the manifold.
When GM wrote the "code" for the PROMs, they designed it around a higher temperture T-stat. When the code sees a lower coolant temperature (along with a low MAT should you have a relocated MAT sensor), the "code" assumes that your engine is warming up, and it overly richens the mixture.
On my SD L98, this code causes the ecm to over compensate on the injector pulse width at lower temperatures thus screwing up any "tuning" you may have done at warmer temperatures. I hate to admit this, but a low temperature Tstat, combined with a relocated MAT and TB bypass (as on my engine) are one of the WORST modifications to make, ESPECIALLY in cooler climates.
The only time these mods MAY benefit you is in +100*F summer weather (to avoid the "Hot Restart" code). But some good tweaking with the PROM can accomplish all that (plus more).
All these time honored "tricks" were when we had no idea what was happening inside the ecm and we were "tricking" the ecm to compensate for our inability to modify the PROM (without an expensive custom PROM).
NOW, that PROM Editors are readily available and the actual equipment is not much more expensive than a cheap (and crappy) "off-the-shelf" Hypercrap, Jet or ADS; do the mod you REALLY should, and that is to burn your own PROM to optimize your engine. It really is the correct solution.
PS: Now that I have looked at some of the PROM code for those "off-the-shelf" sh!ts, I can honestly say that it is the BIGGEST RIP-OFF I have ever seen. What they modify is minimal (a few spark tables, possibly a slightly higer locking speed of your TC and maybe a minor change to the Volumetric Efficiency tables). BUT, I have seen a few (ADS Supersh!t) where they SCREWED UP. ADS transposed some of the numbers in the various tables (you can tell by the general trends) AND they complete forgot to update part of the rpm range for the spark table. Again, when you start looking at their "trends" for a specific MAP reading that you can plainly see the problem.
For what I paid for my ADS Supersh!t, I would have paid for my EPROM Programmer.
Originally posted by LottaBallsCamaro: I'm tring to solve the hot run problem 305 TBI's have. Whats the lowest temp thermastat can I run and still be compatible with the computer? Also, how can you convert to a dual fan setup (like the Z28's).
The *cold* thermostats, are from the flat head ford days.
No reason for em today, they are cover ups ffor poor calibrations, and a cheap work around.
210dF is fine.
Read any of Jenkins, and Yunicks stuff.
If you have to run cold.
Look at a Boat supply place some have 140dF.
Just remember that too cold and no C/L, and possibly no TCC. Depends on your calibration.
In back to back testing I found no difference from 160 to 180 to 195 when tuned correctly
